Gas turbine engines are known, and typically include a fan delivering air into a bypass duct, and into a compressor. The air in the compressor is compressed and passed into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate. The turbine rotors in turn drive the fan and compressor rotors.
Gas turbine engines having a fan as described above are typically utilized to drive aircraft. This fan can be a significant contributor to the noise produced by the aircraft; therefore, quiet fan operation is desired to reduce aircraft noise.